PCOM : A COMPILER FOR A SUBSET OF PASCAL FOR MC68020 UNDER UNIX ENVIRONMENT

Abstract

A compiler for a subset. of Pascal (PLUM) is constructed using the language development tools...Lex, Yacc and Make, available on the UNIX system. It generates target code in MC68020 assembly language for a given source program . This work is divided into four modules. 1. Lexical analyser 2. Parser 3. Error llan•;:1..:~ c and intermediate code generator 4. Code gz_onerator Lexical analyser is generated by giving a .,et of regular expressions as input to Lex. Each regular expression is associated with an action routine for installing lexemes in symbol and literal tables. The grammar for the subset of Pascal is written and given as :Lnpu"t to Ye.cc which in ;u ii 'generates a piar %LCr. . rcor handier and _ er tediacce code generator are implemented by incorporatincj appropriate action program segments in the grammar rules using Syntax Directed Translation. Intermediate code, represented in the form of indirect triples, is divided into basic blocks. It is then converted ir:'.-,o a sequence of MC68020 asserably instruction. Instructions are selected with appropriate addressing modes, to make efficient use of available registers. Register allocation is done based on next use oof the variable in basic block. The .inal code !gerisiated is written to output file gout,